Solvent-Adaptable Poly(vinylpyrrolidone) Binding Induced Anisotropic Shape Control of Gold Nanostructures

Conformational changes in the intrinsic chemical structure of the polymer poly(N-vinyl-2-pyrrolidone) (PVP) in aqueous as well as (in)organic solvents essentially dictates the novel room temperature seedless synthetic procedure for the reduction of hydro-chloroauric acid (HAuCl(4 center dot)3H(2)O) leading to the formation of different anisotropic size/shaped gold nanoparticles. The interaction between gold metal ions and PVP at the given specific monomer to metal ratio leads to sequential metal ligand exchange, thereby simultaneously utilizing the mild reducing property as well as distinct structure-directing/capping ability of PVP in different (in)organic solvents, the synchronized features of which have been carefully explored through NMR and FTIR measurements identifying the foolproof signatures of the polymer coordination interaction for the first time in designing the systematic nucleation and growth/stabilization procedures of anisotropic metal gold nanostructures. Furthermore, the complementary XPS data evaluates the quantitative role of coupled oxygen and nitrogen components of the pyrrolidone ring in the PVP-solvent complex in asserting seedless surface mediation as well as the morphology driven localized surface plasmon suitable for wide range of plasmonic as well as photonic applications.